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In the frequency distribution below the mean is 50 and the total frequency is 120. Class: 0-20, 20-40, 40-60, 60-80, 80-100 Frequency: 17, f1, 32, f2, 19 The missing frequencies f1 and f2 are:

1. 28, 24
2. 24, 36
3. 36, 28
4. None of these

Correct answer: 28, 24

Solution

From total frequency f1 + f2 = 52, and from the mean condition 3f1 + 7f2 = 252; solving gives f1 = 28, f2 = 24.

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